1. Field of the Invention
This invention relates to devices for measuring the specific gravity of a fluid.
2. Description of the Prior Art
Densimeters are well known and have been used for many years to measure the specific gravity of fluids. For measuring the specific gravity of liquid in a battery, hydrometers are used which include a float in a hollow tube. As the fluid is drawn up into the tube the float seeks a level in the fluid proportional to the specific gravity of the fluid. Various types of hydrometers are shown in U.S. Pat. Nos. 1,898,903; 2,674,119; and 2,674,120. A densimeter for measuring the specific gravity of a moving stream of fluid is shown in U.S. Pat. No. 2,332,807. There are many applications in which these devices are not suitable. For example, when the specific gravity of an opaque fluid such as petroleum or milk is needed, the indicator of the device must be such that it can be read without regard to the petroleum or milk or through a foam build-up of each. Also the hydrometer of the U.S. Pat. No. 1,898,903 is not practical with large, deep containers such as tank cars because it would have to be mounted at the top of the car. Consequently, a densimeter is needed that can be used with a wide range of fluids and in hard to reach locations. Another problem is involved with moving fluids. The response of the densimeter must not follow the motion of the fluid. The hydrometer of U.S. Pat. No. 2,674,119 has serrated edges which will interact with the stream of fluid. Also, the device of U.S. Pat. No. 2,332,807 could not be used directly in a moving stream of fluid because its response would correspond to the hydrodynamic forces.